1. Field of the Invention
The present invention relates to semiconductor processing methods and systems of using the semiconductor processing methods.
2. Description of the Related Art
With advances associated with electronic products, semiconductor technology has been widely applied in manufacturing memories, central processing units (CPUs), liquid crystal displays (LCDs), light emission diodes (LEDs), laser diodes and other devices or chipsets. In order to achieve high-integration and high-speed goals, dimensions of semiconductor integrated circuits continue to shrink. Various materials and techniques have been proposed to achieve these integration and speed goals and to overcome manufacturing obstacles associated therewith.
In addition, since wafer sizes gradually increase from 6 inch, 8 inch, 12 inch and even to 16 or 18 inch, more dies can be formed on a single wafer. For example, a 12-inch wafer can provide 2.25 times the number of dies formed from an 8-inch wafer. The increasing wafer size, however, results in concerns associated with the ability to maintain uniformity of various characteristics (e.g., thin film thickness, etch rate, resistance or the like) for layers and structures formed over the wafer. Due to the non-uniformity of substrate characteristics, devices, diodes or circuits formed over the same wafer, but at different locations (e.g., central region and peripheral region) may have different electrical characteristics. However, if the electrical characteristics of dies are substantially different from default levels or fall out of pre-defined specifications, the dies are considered failed, and the yield of the substrate declines. Accordingly, uniformity of substrate characteristics has become an issue to be solved in the field.
FIG. 1 is a drawing showing a prior art method of adjusting processing conditions.
Referring to FIG. 1, a tool 100, such as a chemical vapor deposition (CVD) tool is provided. A wafer (not shown) is placed in the CVD tool 100 for forming a thin film layer (not shown) thereover. Step 110 applies a recipe to the tool 100 for processing the wafer. After the formation of the thin film layer, the wafer is transferred to a measuring tool (not shown) in which step 120 is performed. In step 120, the measuring tool measures the thickness of the thin film layer. The thickness of the film layer is then compared with a desired value of the film layer. In step 130, the comparison result is then fed back to step 110 for adjusting the processing conditions for subsequent substrates. If the measured thickness is larger or less than the desired value, processing conditions are adjusted to form thin film layers with the desired value over subsequent wafers.
The prior art method, however, is not time effective. For example, a second wafer must wait for the measured thickness to be collected from the first wafer, such that a film layer with an ideal desired thickness can be formed over the second wafer. In other words, the second wafer or other subsequent wafers cannot be processed until the measured thickness is collected. If every single wafer fabrication process must go through the loop shown in FIG. 1, time is wasted while an immediately subsequent wafer is idle, waiting for the measured thickness retrieved from the last processed wafer.
In addition, the tool 100 cannot dynamically adjust the processing conditions for providing uniform substrate characteristics. For example, gas or plasma for forming a film layer is uniformly distributed over the wafer. If it is found that non-uniformity of substrate characteristics occurs in the wafer, the electrode or plate that uniformly provides gas or plasma is disassembled and another electrode or plate is substituted that provides a distribution profile corresponding to the measured non-uniform thickness. However, if another measured non-uniformity is collected, another electrode or distribution plate corresponding thereto should be assembled to the tool 100. Not only is the tool 100 unable to dynamically respond to the changing non-uniform profiles, but also disassembling and assembling different electrodes or gas distribution plates increase processing time.
From the foregoing, a method for processing wafers and systems for performing the methods are desired.